JP2899771B2 - Production method of double-sided cast coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast-coated paper used for high-quality printed materials such as catalogs, brochures, company information, and photo magazines, and more particularly to a double-sided cast-coated paper that requires the same high-quality printing on both sides. It is.

[0002]

2. Description of the Related Art Methods for producing cast coated paper include a wet casting method, a gelling casting method and a rewetting casting method. Of these, the rewet casting method involves drying the paint coated on the paper in advance, then applying a rewetting liquid containing water as a main component to the dry paint surface, swelling and plasticizing the paint, and then forming a mirror-like surface. This is a method for obtaining a smooth, high-gloss cast-coated paper by pressing against a polished cast drum and drying, and has a feature that the production speed is higher than that of a wet method or a gelling method. Further, the production of the double-sided cast-coated paper comprises a second step of winding the coated paper after the completion of the first step of forming the cast coat layer on one side, and subsequently forming the cast coat layer on the opposite side. .

[0003] In the production of double-sided cast-coated paper, the cast coating surface in the first step is easily formed by a general coating composition of a conventionally known cast-coated paper, but the second side has a second coating layer. When passing through the two-step cast drum, the drum surface temperature is heated to 95 ° C. or higher, so that when the moisture in the rewetting liquid becomes water vapor and passes through the first and second coating layers and volatilizes, If the air permeability is poor, the vaporized water vapor cannot pass through the paint layer, and blisters in the paper layer called blisters, that is, a paper layer or delamination phenomenon occurs. In order to prevent blisters, the temperature of the cast drum must be lowered to suppress the sudden generation of water vapor. It causes troubles such as defects. In order to prevent such troubles, the speed had to be greatly reduced and productivity was poor, so it was hardly produced. Generally, the first step was a normal calender coating layer, Coated paper that has been cast coated in only two steps has been supplied as cast coated paper.

[0004]

In recent years, cast-coated paper for high-grade printing has been produced using a double-sided cast-coated paper that can be printed in the same manner using the same printing ink on both sides.
And the demand from the market came to be issued. It is desirable that double-sided cast-coated paper that meets such demands be manufactured by coating the same paint on both sides.However, in order to avoid the occurrence of blistering at the time of manufacture, the productivity deteriorates, and inorganic pigments in the paint are deteriorated. There is a method of selecting a particle having a large particle size of the above, but there is a problem that the strong gloss required most for cast coated paper is impaired. An object of the present invention is to provide a method for producing a double-sided cast coated paper having the same printability on both sides while maintaining good productivity without causing a blister phenomenon.

[0005]

Means for Solving the Problems In order to achieve the above object, the present invention has been made as a result of various studies on a method for producing double-sided cast coated paper. In producing the cast-coated paper by the re-wet method, the characteristic values before coating were examined. As a result, the air permeability was determined by the Gurley method (JIS P
8117. ) Is desirably 1000 seconds or less, and even when a cast coat layer is formed on one side, if the air permeability by the Gurley method is 1000 seconds or less, the blister phenomenon does not occur and the gloss and smoothness of the cast coat surface are reduced. It can be seen that the object can be achieved without impairment. In particular, when the single-sided cast coated paper is finished in the first step, the air permeability is 1000 seconds or less, and the glossiness of blank paper (JIS
75 ° specular gloss test method according to P 8142)
This is a result of a study on paints, particularly pigments and their blends, of 0% or more.

[0006] The paint for cast coat comprises a pigment, an adhesive bonding the pigment, and auxiliary agents such as a dispersant, an antifoaming agent, and a release agent. The pigments used include inorganic pigments and organic pigments. As inorganic pigments, there are clay, which is a purified natural mineral pigment, talc, ground calcium carbonate, satin white which is a composite synthetic pigment, titanium oxide which is a semi-synthetic pigment, precipitated calcium carbonate, aluminum hydroxide, and the like.
Organic pigments are also called plastic pigments, which consist of only a single resin such as styrene and urea resin, and those with a double structure with styrene as the core and acrylate, methyl methacrylate, acrylonitrile, butadiene, etc. arranged around the periphery. A resin having an adhesive function, which covers the outer periphery, has also been used as a binder pigment, and many organic pigments such as a hollow structure and a double core-sheath structure have been put on the market.

As the inorganic pigment used in the paint for cast coat, kaolin has excellent whiteness and glossiness, and the present invention has been studied by using a paint using kaolin as a main pigment. However, the smaller the particle size of kaolin, the better the whiteness and glossiness, but the air permeability of the paper after forming the cast coat on one side becomes poor, and the blister phenomenon occurs. When this kaolin is used as the main pigment, a pigment that improves air permeability is selected. As a result, when a precipitated light calcium carbonate (hereinafter abbreviated as calcium carbonate) is blended, a porous coating layer is formed to form a porous coating layer. The water permeability is improved and the water vapor permeability is improved, and among the organic pigments, the urea resin-based organic pigment improves the air permeability in the same manner as calcium carbonate. The properties are good, but the glossiness is poor and the properties as cast coated paper are lost.As a result of further investigation, when aluminum hydroxide is added, calcium carbonate or urea resin organic pigment must be added. Improves impaired gloss,
Furthermore, when aluminum hydroxide and a urea resin-based organic pigment or calcium carbonate are mixed in an amount of 40% by weight or more, it is found that the blister phenomenon does not occur and the productivity is improved, thereby achieving the object.

The air permeability is greatly affected by the coating amount of the paint. However, when the coating amount on one side is 25 g / m ² or more, the glossiness of white paper (75 ° specular glossiness test method according to JIS P 8142) is reduced. Although good, the air permeability is poor, and when the coating amount is 20 g / m ² or less, the air permeability is good, but it is difficult to maintain the blank glossiness of 80%.
Good results as cast coated paper were obtained based on a coating amount of 20 g / m ² .

[0009]

Embodiments of the present invention will be described based on examples. Here, aluminum hydroxide (abbreviated as aluminum hydroxide in the table) as an inorganic pigment is Higlylite manufactured by Showa Denko KK, H-4 having an average particle diameter of 1.0 μm.
H-42 of 3 μm and 0.6 μm, and calcium carbonate was 1.5 μm in average major axis having a columnar particle shape of Okutama Industry Co., Ltd.
m, Tamapearl TP-123, T having a minor axis of 0.3 μm or less
P-HGA015 used Eupar C-122 of Mitsui Toatsu Co., Ltd. as a urea resin-based organic pigment.

Tables 1 and 2 show Examples and Comparative Examples. In the paint formulations shown in the table, the pigment blending ratio is shown by weight%, the auxiliaries are shown by weight percent of solids relative to the pigment, and the binder by weight percent solids relative to the pigment.

[Table 1]

[Table 2]

In the paints shown in Tables 1 and 2, the pigment is 100, and the auxiliaries and binders are% by weight of the pigment. The coating compositions of Examples 1, 3, 5, 7, 9, 11 and Comparative Examples 1 and 3, to which Eupearl was added, had a solid content of 40% due to high viscosity, and the other compositions had 45%. Created. Was coated with an air knife coater so that the 20 g / ^{m 2} on a high-quality paper of the surface of the basis weight of 100 g / ^{m 2} of the coating material in solid, linear pressure 150 kg / cm, diameter 500m
m and a cast drum having a diameter of 1500 mm heated to a predetermined temperature and cast and wound by a rewet casting method using an aqueous solution of zinc sulfate or calcium formate as a rewetting liquid. At this time, the processing speed was 70 m / min, the glossiness was 83 to 88%, and the air permeability of the single-sided cast coated paper was 530 to 980 seconds using Gurley. As a second step, Table 1,
The coating material of No. 2 is coated in the same manner, and rewet casting is performed. The drum temperature was adjusted in two stages as shown in Tables 1 and 2 in consideration of blister generation. The processing speed was adjusted in the range of 45 to 35 m / min in order to prevent the picking strength of the paint surface from being lowered due to the lowering of the drum temperature. When passing through the cast drum in the second step, no blistering occurred, and a double-sided cast coated paper having a good picking strength without a pinhole and a glossiness of 83 to 88% was obtained.

[0012]

Comparative Example Table 2 shows Comparative Examples 1, 2, 3, and 4. When the total value of aluminum hydroxide and urea resin-based organic pigment or calcium carbonate having good air permeability is 40% or less, the air permeability of the single-sided cast coated paper at the end of the first step is 1
If it exceeds 2,000 seconds, the vaporization of water vapor becomes poor and blisters are generated. To prevent this, set the drum temperature to 10
Even at 0 to 95 ° C., not only could the blisters not be suppressed, but also the picking strength of the paint surface in the second step was poor.

[0013]

As described above, since the present invention is a double-sided cast coated paper manufactured using the same paint on both sides, high-grade printing can be performed using the same printing ink on both sides, and the same is applied to both sides. It can be used for high-quality printed materials such as automobile catalogs, mail-order brochures, and company information that require printing effects.

Claims (1)

(57) [Claims] 1. A coating material is coated on one side of paper, and after drying, the coating material is swelled and plasticized with a rewetting liquid , and then pressed against a mirror-polished heat drum to form a highly glossy cast coat surface.
The first step by the rewetting method and the single-sided key obtained in the first step
Similarly, the uncoated surface of cast-coated paper is
In the method for producing a double-sided cast coated paper comprising a second step of forming a last coat surface , the first step and the second step
The paint composition to be applied is the same, and the pigment in the paint is kaolin
The main pigment and to 40% by weight of the total pigment aluminum hydroxide and urea resin-based organic pigment or precipitated calcium carbonate
A method for producing a double-sided cast-coated paper, characterized by being blended as described above .